Machado, J. A. TenreiroGalhano, Alexandra2014-06-252014-06-2520090924-090X1573-269Xhttp://hdl.handle.net/10400.22/4582The theory of fractional calculus goes back to the beginning of the theory of differential calculus, but its application received attention only recently. In the area of automatic control some work was developed, but the proposed algorithms are still in a research stage. This paper discusses a novel method, with two degrees of freedom, for the design of fractional discrete-time derivatives. The performance of several approximations of fractional derivatives is investigated in the perspective of nonlinear system control.engFractional calculusControlDiscretization schemesjournal article10.1007/s11071-008-9409-4